This invention relates to a valve for limiting the flow of hot fluid from an operational chamber of a rotor along a flow path defined by the clearance of a shaft and the housing of the rotor.
In jet engine powered aircraft it is common practice to use hot compressor discharge air as the motive force for air motors used to operate various controls. The temperature of such compressor discharge air on entering an air motor often exceeds 1100.degree. F. In order to permit the components of the air motor to expand in response on exposure to such hot compressor discharge air, large clearances are provided between the shaft of the rotor and the housing of the air motor.
Unfortunately, such large clearance allows a portion of the hot compressor discharge air to flow to the surrounding environment reducing the efficiency of the rotor in addition to raising the temperature of the bearings of the rotor. High rotational speeds and operational temperatures preclude rubbing contact seals to eliminate such loss of hot fluid through the clearance since such seals adversely increase the drag on the rotor to further reduce efficiency of the air motor.
Labyrinth seals have been used to reduce the leakage of the hot fluid through such clearance. However, labyrinth seals are relatively ineffective at high pressures and when used in air motors permit sufficient hot compressor discharge air to flow through the clearance to adversely affect the bearings.
U.S. patent application Ser. No. 958,590, filed Nov. 7, 1978, and now U.S. Pat. No. 4,276,006, discloses a system for cooling the bearings in the rotor of an air motor. Unfortunately, when the rotor is being operated at a high speed with high pressure compressor discharge air, the air flow being drawn through the bearings could be reduced by an increase in volume of the compressor discharge air flow through the clearance. This can reduce the effectiveness of such a cooling system.